DESCRIPTION: (Applicant's Description) The Statistical Sciences Core (SSC) will be responsible for providing support and methodological leadership to TTURC investigators in the design, development and implementation of all three major research projects (IUE, AP, ST) as well as current(CR, YAI) and future developmental projects. To this effect, the SSC will (a) ensure that studies are designed with cleary defined and scientifically important objectives, study goals are operationally feasible, and study results are carefully analyzed and sensibly interpreted, (b) develop and maintain a primary study database and implement an efficient, secure and accurate mechanism for on-line access to the database by SSC personnel for purposes of study monitoring and analysis, (c) monitor and verify the quality of the data, including checks of accuracy, (d) support investigators in all participating institutions in their efforts to access the primary database and to perform on-site data analyses and (e) address methodological issues arising in the design and analysis of TTURC studies and to carry out research on statistical methodology for the construction and evaluation of risk profiles for lifetime progression to nicotine dependence, based on information on premorbid and comorbid risk factors culled from the Providence and Boston cohorts of the National Collaborative Perinatal Project.